function getLocalFilePath(path) {
  if (path.indexOf('_www') === 0 || path.indexOf('_doc') === 0 || path.indexOf('_documents') === 0 || path.indexOf('_downloads') === 0) {
    return path
  }
  if (path.indexOf('file://') === 0) {
    return path
  }
  if (path.indexOf('/storage/emulated/0/') === 0) {
    return path
  }
  if (path.indexOf('/') === 0) {
    var localFilePath = plus.io.convertAbsoluteFileSystem(path)
    if (localFilePath !== path) {
      return localFilePath
    } else {
      path = path.substr(1)
    }
  }
  return '_www/' + path
}

export function pathToBase64(path) {
  return new Promise(function(resolve, reject) {
    if (typeof window === 'object' && 'document' in window) {
      if (typeof FileReader === 'function') {
        var xhr = new XMLHttpRequest()
        xhr.open('GET', path, true)
        xhr.responseType = 'blob'
        xhr.onload = function() {
          if (this.status === 200) {
            let fileReader = new FileReader()
            fileReader.onload = function(e) {
              resolve(e.target.result)
            }
            fileReader.onerror = reject
            fileReader.readAsDataURL(this.response)
          }
        }
        xhr.onerror = reject
        xhr.send()
        return
      }
      var canvas = document.createElement('canvas')
      var c2x = canvas.getContext('2d')
      var img = new Image
      img.onload = function() {
        canvas.width = img.width
        canvas.height = img.height
        c2x.drawImage(img, 0, 0)
        resolve(canvas.toDataURL())
        canvas.height = canvas.width = 0
      }
      img.onerror = reject
      img.src = path
      return
    }
    if (typeof plus === 'object') {
      plus.io.resolveLocalFileSystemURL(getLocalFilePath(path), function(entry) {
        entry.file(function(file) {
          var fileReader = new plus.io.FileReader()
          fileReader.onload = function(data) {
            resolve(data.target.result)
          }
          fileReader.onerror = function(error) {
            reject(error)
          }
          fileReader.readAsDataURL(file)
        }, function(error) {
          reject(error)
        })
      }, function(error) {
        reject(error)
      })
      return
    }
    if (typeof wx === 'object' && wx.canIUse('getFileSystemManager')) {
      wx.getFileSystemManager().readFile({
        filePath: path,
        encoding: 'base64',
        success: function(res) {
          resolve('data:image/png;base64,' + res.data)
        },
        fail: function(error) {
          reject(error)
        }
      })
      return
    }
    reject(new Error('not support'))
  })
}

export function base64ToPath(base64) {
  return new Promise(function(resolve, reject) {
    if (typeof window === 'object' && 'document' in window) {
      base64 = base64.split(',')
      var type = base64[0].match(/:(.*?);/)[1]
      var str = atob(base64[1])
      var n = str.length
      var array = new Uint8Array(n)
      while (n--) {
        array[n] = str.charCodeAt(n)
      }
      return resolve((window.URL || window.webkitURL).createObjectURL(new Blob([array], { type: type })))
    }
    var extName = base64.match(/data\:\S+\/(\S+);/)
    if (extName) {
      extName = extName[1]
    } else {
      reject(new Error('base64 error'))
    }
    var fileName = Date.now() + '.' + extName
    if (typeof plus === 'object') {
      var bitmap = new plus.nativeObj.Bitmap('bitmap' + Date.now())
      bitmap.loadBase64Data(base64, function() {
        var filePath = '_doc/uniapp_temp/' + fileName
        bitmap.save(filePath, {}, function() {
          bitmap.clear()
          resolve(filePath)
        }, function(error) {
          bitmap.clear()
          reject(error)
        })
      }, function(error) {
        bitmap.clear()
        reject(error)
      })
      return
    }
    if (typeof wx === 'object' && wx.canIUse('getFileSystemManager')) {
      var filePath = wx.env.USER_DATA_PATH + '/' + fileName
      wx.getFileSystemManager().writeFile({
        filePath: filePath,
        data: base64.replace(/^data:\S+\/\S+;base64,/, ''),
        encoding: 'base64',
        success: function() {
          resolve(filePath)
        },
        fail: function(error) {
          reject(error)
        }
      })
      return
    }
    reject(new Error('not support'))
  })
}